In general, high temperature components of gas turbine generators which is being operated at a temperature of 1,100° C. or greater may be exposed to high-temperature and high-pressure combustion gas and have been used in environmental conditions where a mechanical stress is applied by 3,600 revolutions per minute (RPM).
In particular, since gas turbine generators are operated while a starting-up operation and a stopping operation thereof are repeated every day, the high temperature components may be repeatedly heated and cooled, whereby inherent material characteristics of the high temperature components may be further rapidly degraded.
In order to prevent a deterioration in material characteristics of the high temperature components, in the case of a component fabricated using a further excellent material or a surface-treated component, it may be required to prove stability of the component by performing a test thereon before it is actually applied to the gas turbine generators.
Among tests for examining stability of components, a representative example may be a heat cycle test.
That is, the heat cycle test may be conducted by repeating a step in which a user directly inputs specimens in a space maintained at high temperature and takes out the specimens therefrom after the elapse of a predetermined time to thereby cool the specimens, or by using an apparatus for testing thermal fatigue or an apparatus for testing thermal tension.
However, it may be infeasible to perform thermal fatigue and tension tests at an actual operating temperature of a gas turbine, it may be unviable to test several specimens under the same conditions, and the rapid cooling of the specimens may be difficult.
As the related art technology for solving the above problem, Korean Utility Model Registration Publication No. 20-0406102 teaches “an apparatus for testing thermal fatigue”.
In Korean Utility Model Registration Publication No. 20-0406102, FIG. 1 is a conceptual diagram schematically illustrating the apparatus for testing thermal fatigue.
Referring to FIG. 1 of Korean Utility Model Registration Publication No. 20-0406102, an apparatus 10 for testing thermal fatigue according to the related art may be provided to measure thermal fatigue strength of a high temperature component specimen used in a gas turbine generator, and may include a tube furnace 1 heating specimens (not shown) to high temperature, a cooling part (not shown) rapidly cooling the heated specimens to room temperature, a specimen transferring element allowing the specimens to be installed thereon and transferring the specimens to the tube furnace 1 or the cooling part, and a controlling unit controlling temperatures and times of the tube furnace 1 and the cooling part and the repeated numbers of times.
In addition, the specimen transferring element may include a specimen mounting part 7 allowing the specimens to be mounted thereon and transferring the specimens to the tube furnace 1 and the cooling part, and an air cylinder part 5 driving the specimen mounting part 7, and the cooling part may include an air compressor 3 and a compressed air spraying nozzle 4.
That is, in the apparatus 10 for testing thermal fatigue according to the related art, after six specimens are simultaneously mounted in holes of the specimen mounting part 7, a switch of a control panel 8 may be operated to drive the air cylinder part 5, and the specimen mounting part 7 may be carried into a quartz pipe 2.
In this state, the specimens are maintained at high temperature for a preset time as required. After the elapse of the preset time, the specimen mounting part 7 may be taken out and may be transferred to a lower portion of the compressed air spraying nozzle 4 connected to the air compressor 3.
In this state, compressed air may be sprayed out and may be rapidly cooled to room temperature. The heating and cooling is regarded as a single cycle and the heating and cooling may be repeatedly performed in required numbers of cycles.
However, in the apparatus 10 for testing thermal fatigue according to the related art, since a test specimen is heated at the same temperature over an overall thickness thereof, time required for reaching thermal fatigue fracture may be extended, such that test efficiency may be significantly deteriorated.
Moreover, in the apparatus 10 for testing thermal fatigue according to the related art, during a thermal fatigue test, a laser beam or flames are used as a thermal source to directly heat a coating layer, and an opposite side of the test specimen may be cooled by spaying compressed air thereto or bringing the opposite side into contact with a block in which cooling water circulates, such that a thermal gradient may be applied. However, in this case, it may be difficult to control a flame temperature and positon and costs required for manufacturing the apparatus and examining a test may be disadvantageously high.